新型電極結構於提升負型液晶垂直配向邊緣場效驅動性能之研究

Abstract

近年來，液晶顯示器對高速反應與高亮度的需求日益提升，其中三階電極之3D VA-FFS結構因具備優異的光穿透率與響應速度，其發展潛力可望成為未來液晶顯示技術的重要研究方向。本實驗室近年提出之挖洞式六邊形排列結構，雖可透過增加孔洞周圍的虛擬牆數量，有效提升液晶的反應速度，然而該結構在孔洞區域內易產生明顯暗區，影響整體顯示亮度，且在小尺寸電極條件下亦存在虛擬牆穩定性不足的問題，導致虛擬牆產生位移甚至破壞，進而造成元件操作異常，成為進一步發展的技術瓶頸。 為解決上述問題，本論文首先提出於像素電極所挖設之圓形孔洞內，在距離孔洞圓心一定距離處添加若干小面積電極的設計。藉由強化孔洞內部局部電場強度，可對液晶分子施加更大的相位延遲，進而提升其轉動角度。實驗結果顯示，此設計能有效降低孔洞區域的暗區面積，改善局部穿透率曲線中的凹陷現象，並提升整體亮度表現。雖此方法伴隨反應時間略有延長，惟其影響幅度極小，屬可接受範圍內，整體顯示效能仍具顯著改善。 此外，為解決挖洞式六邊形排列結構於小尺寸電極條件下，因虛擬牆穩定性不足所導致無法正常運作之問題，本研究進一步引入「反轉結構」設計。藉由其穩定的電場邊界特性，能有效抑制虛擬牆之位移現象，顯著提升結構於小尺寸條件下的操作穩定性，並實現相較於大尺寸電極更為快速的反應速度。但由於反轉結構電極面積較小，需施加較高操作電壓方能驅動液晶達到最大光穿透率，為此本論文透過同步下調電壓之方式，在不改變電極層間電壓差的前提下，成功將整體操作電壓降低至原先之一半，同時仍能維持與原設定相當之穿透率與反應時間表現。

In recent years, the demand for high-speed response and high brightness in liquid crystal displays has been steadily increasing. Among various technologies, the three-electrode 3D VA-FFS structure has emerged as a promising development due to its excellent optical transmittance and fast response characteristics. Although previous studies have proposed a perforated hexagonal array structure that improves liquid crystal response speed by increasing the number of virtual walls around the holes, this design still suffers from noticeable dark areas within the hole region, degrading overall display brightness. Furthermore, under small electrode configurations, the virtual wall becomes unstable, leading to displacement or collapse, and ultimately causing operational failure. To address these issues, this thesis first proposes a novel design that incorporates several small-area electrodes within the circular holes of the pixel electrode, positioned at a certain distance from the hole center. By enhancing the local electric field strength inside the hole, the liquid crystal molecules experience greater phase retardation, thereby achieving larger rotation angles. Experimental results demonstrate that this design effectively reduces the dark areas in the hole region, improves local transmittance uniformity, and enhances overall brightness. Although a slight increase in response time is observed, its impact is minimal and within acceptable limits, resulting in a net improvement in display performance. In addition, to solve the operational instability of the perforated hexagonal structure under small electrode conditions, this study further introduces a "reversed structure" design. By leveraging its more stable electric field boundary characteristics, the proposed structure effectively suppresses virtual wall displacement and significantly enhances operational stability in small-size electrodes, while also achieving a faster response time compared to larger electrodes. However, due to the smaller electrode area in the reversed structure, a higher operating voltage is required to achieve maximum light transmittance. To mitigate this drawback, a “simultaneous voltage-downscaling” strategy is proposed. This method successfully reduces the overall operating voltage to half of the original value without altering the inter-electrode voltage difference, while still maintaining comparable transmittance and response time performance.